Few investigations have been made on host defense in the male urogenital mucosa. Studies at other mucosal surfaces have shown that innate and early-induced immunological responses provide rapid antimicrobial host defenses which can prevent pathogens establishing infection at a mucosal surface, or control replication until anti-specific cells are recruited locally. Furthermore, recent evidence has highlighted the importance of epithelial cells in providing signals that can initiate and amplify the early mucosal inflammatory response. The defensins are small (<4kd), cysteine-rich, cartionic peptides with a broad spectrum of antimicrobial activity. Recently three novel defensins-human defensin-5 (HD-5, an alpha- defensin, and human beta-defensins 1 and 2 (HBD-1 and -2) have been located in human epithelial cells from various tissues. Their importance in mucosal defense was highlighted when HBD-1 was found to be the major antimicrobial component of airway surface fluid. Although the biological roles of the epithelial defensins have not been extensively investigated, studies with the polymorphonuclear neutrophil (PMNs) defensins indicate that these molecules may have chemo opsonic and wound healing properties in addition to their antimicrobial activity. We recently identified HD-5, HBD-1 and HBD-2 in prostate, seminar vesicles and penile urethra. Preliminary in vivo and in vitro data indicate that HBD-1 is constitutively expressed, but that HBD-2 and HD-5 expression patterns correlate with infectious and inflammatory events. We hypothesize that the epithelial defensins (HD-5, HBD-1 and HBD-2) are a major component of the early urogenital mucosal response to STD pathogen, and the overall goal of this proposed study is to elucidate their expression, secretion and biological activity in the urogenital environment. More specifically, we propose to: (1). Characterize epithelial defensin expression patterns in normal and inflamed prostate, seminal vesicles and penile urethra; (2). Isolate and characterize secreted defensin forms in prostatic fluid and urethral washing of normal men and men with defined STDs; (3). Evaluate the antimicrobial activity of native and recombinant defensin forms to Chlamydia trachomatis, Neisseria gonorrhoeae and HSV-2, and of urogenital epithelial cells to evaluate the role of secreted and intracellular secretions; (4). Establish polarized cultures of urogenital epithelial cells to evaluate the role of secreted and intracellular defensins in pathogen challenge; (5). Determine the chemotactic activity of native and recombinant defensin forms to leukocyte subpopulations, role of epithelial defensins in early events following host-pathogen interaction in the male genital tract, both with respect to direct antimicrobial activity, and interaction with other mediators of the early immune response.